Mobile telephones with exposed keypads may have the disadvantage that during handling of the mobile phone, a key can unintentionally be pressed, thereby causing some sort of undesired action to be taken by the mobile phone. For example, when a mobile telephone is being carried in a user's pocket, a key on the keypad of the mobile phone can accidentally be pressed, causing the mobile phone to initiate a call without the user being aware of it.
Therefore, most mobile phones are equipped with a “key lock” function. The “key lock” function “locks” the keypad when it is not in use in order to prevent unwanted actions from being performed.
This problem has typically been addressed in one of two ways. The first way is to mechanically cover the keypad when it is not in use. The second way is with a software based key lock function.
One example of a phone which makes use of the first way is a clamshell type phone. Clamshell phones are very intuitive for the user to use. However, clamshell phones need to be opened before they can be used, which may be annoying to certain users. Furthermore, clamshell phones may typically be more complex, due to the fact that the phone comprises two parts connected by a hinge. Since electrical signals need to pass through the hinge joint, the hinge joint is usually quite complex. Due to this extra complexity, the robustness of the phone may be reduced. Clamshell phones may also typically be thicker than other types of phones.
Another type of phone which covers the keypad when it is not in use is a mobile phone with a sliding cover. However, the sliding motion required to activate the phone may be rather large, since the entire keypad may need to be uncovered. This large sliding movement may also be annoying to some users. In addition, it may be easy to damage the sliding cover, since it may extend a rather large distance from the phone when the keypad is in its active state.
Recently, another type of phone has been introduced where the phone is split into two parts which are slideably or pivotably connected to each other, and in which the first part contains the keypad and the second part contains the display. However, these types of phones may have a rather complex electro-mechanical interface whereby the part containing the keypad is connected to the main part of the phone. This may increase the cost and/or decrease the robustness of the phone. These types of phones may also typically be thicker than other types of phones.
One example of the second way of providing a key lock function is where the user is forced to push two specific keys in a certain order to activate the phone. For example, the user may need to press the “clear” key followed by the “yes” key. Another way of implementing a key lock function is where the user must hold a certain key down for a certain amount of time. Software based solutions are less intuitive than the mechanical cover element and can confuse some users. It is also possible for the user to forget the combination required to open the phone, which can happen when a user uses multiple phones. Another disadvantage with the software-based key lock routines is that when the phone is in its locked state, each time that a key is accidentally pressed, the key lock routine is activated in order to check if this was an accidental key press or the first event of the unlocking routine. This activity may consume unnecessary battery power. Another problem with software-based methods is that the user may be forced to check the display of the phone in order to see if the key lock is activated. It is not possible to be able to determine the status of the key lock function, for example, just by looking at the phone or by touching the phone
Another type of key lock function is disclosed Japanese Publication JP 2005167455, which discloses an extra key that is used to activate and deactivate the key lock. The key may be a monostable key, that is, it may be spring biased into one position. This is similar to the software based solution, but instead of having to remember a combination or a certain key to press, the user can always activate the same key. However, this solution may have some of the problems mentioned above with respect to the software-based solutions. In addition, since modern mobile phones are becoming smaller and smaller, it may not be desirable to have extra keys cluttering the surface of the mobile phone.